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Umnica [9.8K]
3 years ago
5

How much heat energy is required to melt 75g of ice at 0°C?

Chemistry
1 answer:
Mnenie [13.5K]3 years ago
4 0

The enthalpy change for melting ice is called the entlaphy of fusion. Its value is 6.02 kj/mol. This means for every mole of ice we melt we must apply 6.02 kj of heat. We can calculate the heat needed with the following equation:

Q = N x ΔH

where:

Q  = heat

N  = moles  

ΔH  = enthalpy

In this problem we would like to calculate the heat needed to melt 35 grams of ice at 0 °C. This problem can be broken into three steps:


1. Calculate moles of water

2. multiply by the enthalpy of fusion

3. Convert kJ to J.


Step 1 : Calculate moles of water

[ 75g ] x (\frac{1 mol}{18.02g} ) =

Step 2 : Multiply by enthalpy of fusion

Q = N × ΔH  = <em> [ Step 1 Answer ]</em> ×  6.02 =

Step 3 : Convert kJ to J

[ Step 2 Answer ] x (\frac{1000j}{1kJ} ) =

Finally rounding to 2 sig figs (since 34°C has two sig figs) we get


Q Would Equal ____

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stiks02 [169]

<u>Answer:</u> 0.0237 g of calcium carbonate would be required to neutralize the given amount of HCl

<u>Explanation:</u>

pH is defined as the negative logarithm of hydrogen ion concentration present in the solution

pH=-\log [H^+]      .....(1)

Given value of pH = 1.5

Putting values in equation 1:

1.5=-\log[H^+]

[H^+]=10^{(-1.5)}=0.0316M

Molarity is defined as the amount of solute expressed in the number of moles present per liter of solution. The units of molarity are mol/L. The formula used to calculate molarity:

\text{Molarity of solution}=\frac{\text{Number of moles of solute}\times 1000}{\text{Volume of solution (mL)}}       .....(2)

We are given:

Volume of solution = 15.0 mL

Molarity of HCl = 0.0316 M

Putting values in equation 2:

0.0316=\frac{\text{Moles of HCl}\times 1000}{15.0}\\\\\text{Moles of HCl}=\frac{0.0316\times 15.0}{1000}=4.74\times 10^{-4}mol

The chemical equation for the reaction of HCl and calcium carbonate follows:

2HCl+CaCO_3\rightarrow H_2CO_3+CaCl_2

By the stoichiometry of the reaction:

2 moles of HCl reacts with 1 mole of calcium carbonate

So, 4.74\times 10^{-4}mol of HCl will react with = \frac{1}{2}\times 4.74\times 10^{-4}=2.37\times 10^{-4}mol of calcium carbonate

The number of moles is defined as the ratio of the mass of a substance to its molar mass.

\text{Number of moles}=\frac{\text{Given mass}}{\text{Molar mass}}

Moles of calcium carbonate = 2.37\times 10^{-4}mol

Molar mass of calcium carbonate = 100.01 g/mol

Putting values in the above equation:

\text{Mass of }CaCO_3=(2.37\times 10^{-4}mol)\times 100.01g/mol\\\\\text{Mass of }CaCO_3=0.0237g

Hence, 0.0237 g of calcium carbonate would be required to neutralize the given amount of HCl

7 0
2 years ago
Explain why the process of dissolution can be exothermic or endothermic (heat of solution) with different solutes
RUDIKE [14]

Answer:

The process of dissolving is exothermic when more energy is released when water molecules “bond” to the solute than is used to pull the solute apart. Because more energy is released than is used, the molecules of the solution move faster, making the temperature increase.

Project the image Endothermic Dissolving.

The process of dissolving is endothermic when less energy is released when water molecules “bond” to the solute than is used to pull the solute apart. Because less energy is released than is used, the molecules of the solution move more slowly, making the temperature decrease.

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Ivenika [448]

Answer:

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Explanation:

The zeros before a non zero digit do not count as significant figures so there are 4 sig figs in the number

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Answer:

A. Felsic igneous rocks are less dense than mafic igneous rock

Explanation:

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D, It is a flow of protons, is the best answer. Electricity is the flow of electrons, not protons.
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